Logic Outputs Problem in 7493 IC

_q12x_ · Jan 3, 2023

Hello from Romania.
I have all the counting ccts, for every number. This is counting to 16 and its the last one this 7493 can count.
I encounter a new and very weird problem. All the [Q] (QA,QB,QC,QD) outputs of the 7493 are not so good at outputting. At least to my components I tested so far.

[ElectriciansForums.net] Logic Outputs Problem in 7493 IC

I simulated more possibilities and all failed. I thought maybe the simulator is not that good. But when I tried the BJT in reality, it still didnt work. I really want to believe it will work with opamps in reality, but if it will not work, it means the simulator is right.
I didnt try with mosfets in the simulator yet, they were just prepared there. I didnt test them in cct.
THe problem is the (-) that 'comes out' after these buffering devices. When they are on (-) on their output.

I actually solved the problem using a tri-state buffer. They are the only component that are solving this issue.
Ive also get 10 pcs from aliespress. I start to value them now, when I actually need them. But they will arrive after 2 or so months from now.
- I want to find a solution (IF POSSIBLE) without them, or at least until they arrive.

This cct I already make and it is working fine (in the simulator) is to output a decimal number for all the 16 binary counts.
Pretty much when is 0100 it will lit the 4th LED. When is 1000 the 8th LED and so on, from 1 to 16 (including 0).
You can see in the screenshot already.
I work on this cct and numerous problems for .... about 10 or more days. Very hard to do it alone !!! But I did it. so far.

I even have an easier output method than this very complicated cct I already built.
- Simply to display in binary. Like these 4 LogicProbe from Proteus simulator that I am always take for granted.
So we can do these first !

To make a simple binary counter [LED display], I will still need some sort of buffer, like the ones I specified already.
I wait for your response. This is a very complicated cct and a big problem for me.
Thank you and hope I will get some interesting answers! (mister @marconi , my Logical friend?haha)
And also Happy New Year 2023 to everyone that are reading my posts !

marconi · Jan 7, 2023

Yes I have watched your video which was clear. Construct these two circuits. The left one will light the led when all inputs are logic 1 and the right one inverts the input.

First of all do a decoder for 0011. You will need one copy of the NAND and two copies of the NOT.

Do you have 8 n channel power mosfets?

_q12x_ · Jan 7, 2023

marconi said:
Do you have 8 n channel power mosfets?

I have.
But the thing is.... I progressed until then.
I measured everything with my osciloscope. I wasnt getting a clear HIGH on the 7493 outputs. In fact, I wasnt getting ANY SIGNAL AT ALL. I was getting a very lousy signal, but VERY close to gnd but I think that was some other type of signal, not the real one, because my osciloscope is catching multiple signals at once. So I decided that 7493 either its outputs are not good - because all this diodes arrangement, compromising somehow the outputs to gnd ...
OR
the signal was so fast that the LED #1 didnt had time to react. Maybe everything is working as it should, but if the signal is fast like 1us, like a spike, that doesnt tell anything to the LED what to do and how much to stay lit. Right?
---
I then, did the following experiment: I put a 7474 DTFF on one of the output of the 7493 and run the entire thing.
Very simple setup:

I was counting to 4 I think. So the Led on the 7474 output, was litting and staying lit until the next count. (UNFORTUNATELY)
like so: 1234 - led ON and staying ON, 1234- led OFF and staying off, and again....
It should have be: 12 -led ON - 3-Led OFF 4 and repeat the same sequence again. But it wasnt.
BUT
This prove a point. That the outputs of the 7493, in the current configuration, with those diodes there, can be expanded to other inputs IC. And als othat the signal is ok and also that is as I suspected, VERY-VERY FAST. Too fast for the LED to know what to do. Thats a problem !!! And I intend to find a solution.
Momentarily I am thinking on a DELAY solution using a 555 per 1one line for the moment. But if it will work, I will have to put 4 of them for each line.
Also VERY important to mention ! If until this experiment right now, I was NOT getting any clear osciloscope readings on any of those 4 lines (when they were all connected to the NOT IC and after that to the LED...) NOW, I get a CLEAR 5V HIGH and 0 LOW. Using the Flip Flop version. But Im starting to see the picture. I hope you will agree with my observations.
Pretty much what Im doing right now is a binary display for ONLY these 4 wires here.
IF you know any way of DELAY-ing the signal, to slow it down to... I dont know, 100ms maybe? enough that the LED will flash ON, that will be great. I am planning to use a 555 for 1 line for now. If this will work, we're in bizniz.
Tell me what you think.

marconi · Jan 7, 2023

If you have 8 n channel power mosfet then but these can be connected common source to the 0V rail and a 1kR resistor inserted between each drain and the 5V rail.

Four of the mosfet have their gates driven by A, B ,C and D outputs of the 7493 and the other four by A*, B*, C* and D* derived from the four inverter gates you currently use. You can dispense with the 4 pnp transistors.

Connect the first 4 mosfet drains to the current logic busbars and the second 4 mosfets drains to a new set of 4 logic busbar. Now you can connect the 4 input dtl NAND with led as required to 4 of these 8 busbar to select the right 4 term logic operand term for the led. The eight busbars provide A, B, C, D, A*, B*, C* and D* the logic signals.

With this scheme you can avoid using dtl NOT gates.

marconi · Jan 7, 2023

_q12x_ said:
I have.
But the thing is.... I progressed until then.
I measured everything with my osciloscope. I wasnt getting a clear HIGH on the 7493 outputs. In fact, I wasnt getting ANY SIGNAL AT ALL. I was getting a very lousy signal, but VERY close to gnd but I think that was some other type of signal, not the real one, because my osciloscope is catching multiple signals at once. So I decided that 7493 either its outputs are not good - because all this diodes arrangement, compromising somehow the outputs to gnd ...
OR
the signal was so fast that the LED #1 didnt had time to react. Maybe everything is working as it should, but if the signal is fast like 1us, like a spike, that doesnt tell anything to the LED what to do and how much to stay lit. Right?
---
I then, did the following experiment: I put a 7474 DTFF on one of the output of the 7493 and run the entire thing.
Very simple setup:
View attachment 105101
I was counting to 4 I think. So the Led on the 7474 output, was litting and staying lit until the next count. (UNFORTUNATELY)
like so: 1234 - led ON and staying ON, 1234- led OFF and staying off, and again....
It should have be: 12 -led ON - 3-Led OFF 4 and repeat the same sequence again. But it wasnt.
BUT
This prove a point. That the outputs of the 7493, in the current configuration, with those diodes there, can be expanded to other inputs IC. And als othat the signal is ok and also that is as I suspected, VERY-VERY FAST. Too fast for the LED to know what to do. Thats a problem !!! And I intend to find a solution.
Momentarily I am thinking on a DELAY solution using a 555 per 1one line for the moment. But if it will work, I will have to put 4 of them for each line.
Also VERY important to mention ! If until this experiment right now, I was NOT getting any clear osciloscope readings on any of those 4 lines (when they were all connected to the NOT IC and after that to the LED...) NOW, I get a CLEAR 5V HIGH and 0 LOW. Using the Flip Flop version. But Im starting to see the picture. I hope you will agree with my observations.
Pretty much what Im doing right now is a binary display for ONLY these 4 wires here.
IF you know any way of DELAY-ing the signal, to slow it down to... I dont know, 100ms maybe? enough that the LED will flash ON, that will be great. I am planning to use a 555 for 1 line for now. If this will work, we're in bizniz.
Tell me what you think.

Qc changes every 4 clock pulses. This is correct. See count sequence table bottom right on page 3 of:

https://www.ti.com/lit/ds/symlink/sn74ls93.pdf?ts=1673101430824&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FSN74LS93

You have a connection Qc to reset RO1 - why? I thought you wanted to count in binary from 0 to 15 and then back to 0 and repeat?

I think you line of thought about fast pulses is a red herring. If you doubt that the 93 is working correctly then it is simple enough to test it.

_q12x_ · Jan 7, 2023

I didnt know this image you show with the 4 clocked output pulses ! Very interesting indeed. Thanks for it. It didnt cross my mind to search for it either! You did good (this time). Haha. I actually save it in my 7493 folder. It is extremely important to actually see the ------- how is working by default. Im learning...

marconi said:
You have a connection Qc to reset RO1 - why? I thought you wanted to count in binary from 0 to 15 and then back to 0 and repeat?

Well, Like I said, and also explained in my movie as well and SHOW it there very clearly.... but I will repeat, no problem, I am using this cct as 2 parts, 1=the logic and 1=the display. So in the logic part I have this counter 0-15. But I will change it, manually, depending what number I will need to count. I used some examples, including the maximum of count to 16. But it can be 1by1 count as well. Depends what I will need when I will need it. Get me?
The display part SHOULD do its job for whatever count # I SET. Simple.

marconi said:
If you doubt that the 93 is working correctly then it is simple enough to test it.

I already did, using that DTFF I mentioned earlier. The 7493 is fine. The pulse from it is not fine for the type of output I want to use.
The very FAST pulse that my golden osciloscope can not read it at all, (only the 7474 DTFF did) is most probably because of the strange connections with the diodes directly to each Q output of the 7493. Thats why the fast signal, like a spike. It would have being nice to be like in your 4 clock pulses picture !!! But it isnt.

_q12x_ · Jan 7, 2023

marconi said:
If you have 8 n channel power mosfet then but these can be connected common source to the 0V rail and a 1kR resistor inserted between each drain and the 5V rail.

Four of the mosfet have their gates driven by A, B ,C and D outputs of the 7493 and the other four by A*, B*, C* and D* derived from the four inverter gates you currently use. You can dispense with the 4 pnp transistors.

Connect the first 4 mosfet drains to the current logic busbars and the second 4 mosfets drains to a new set of 4 logic busbar. Now you can connect the 4 input dtl NAND with led as required to 4 of these 8 busbar to select the right 4 term logic operand term for the led. The eight busbars provide A, B, C, D, A*, B*, C* and D* the logic signals.

With this scheme you can avoid using dtl NOT gates.

I cant say I clearly understand ALL that you said here.
You are more clear in drawing cct than writing !!!
But I get the hint from your reading here, even if I dont completely understand it. To use mosfets as HIGH and LOW switching for the 4line bus. And most probably the other 4 you mention to be the 0V gate discharge. Its how I see it.
I will draw a quick cct of how ---I--- believe this should be. If its exactly as you explained here, then my sub-conscientious brain understood it, not the conscientious one. Haha.
Update soon.

_q12x_ · Jan 7, 2023

I believe like this should work...

marconi · Jan 8, 2023

_q12x_ said:
I cant say I clearly understand ALL that you said here.
You are more clear in drawing cct than writing !!!
But I get the hint from your reading here, even if I dont completely understand it. To use mosfets as HIGH and LOW switching for the 4line bus. And most probably the other 4 you mention to be the 0V gate discharge. Its how I see it.
I will draw a quick cct of how ---I--- believe this should be. If its exactly as you explained here, then my sub-conscientious brain understood it, not the conscientious one. Haha.
Update soon.

No that’s not what I meant. I will draw the idea soon.

marconi · Jan 8, 2023

If you were to use the 'standard' forms of DTL gates (my #16) I sent you examples of then my later idea was to generate A, B, C, D and A*, B*, C* and D* using the circuit attached. You then connect the 4 inputs to the appropriate busbar for the LED you want to light at a particular state of the 93's Q outputs.

I suspect - please confirm - that you are determined to (try to) make your version of DTL logic gates to work - therein lies most of the problem - they are not good designs and will have difficulty working alongside each other when connected to the logic busbars because they interact and this gets worse the more of them are connected to the busbars.

I would have 4 LEDs indicating the 93's Q outputs state to aid seeing what is happening.

Whether you have other problems/defects on your breadboards I have difficulty fathoming without them in front of me.

marconi · Jan 8, 2023

Ok, Try implementing the circuitry below for each Q output. It will produce for each Q output the option of sinking or sourcing current. Your DTL logic gates require for some inputs to be sourced and for the other to be sinked. I have illustrated this.

_q12x_ · Jan 8, 2023

I modified your picture and interpret it my way.
Its an interesting idea... IF those mosfets will work as I planned in my #22.
Currently I have problems interfacing 1 single wire with 1 single led. Nothing worked so far (in reality). Only in the blody simulator.
Thats the problem....
Your idea will be 'plan B' if the 4 wires will not be enough and get errors on all those 16 # LEDs.

In the meantime I solved in the simulator the 555 delay problem... I have to try it in reality. Hope it works. Cross your balls for me.

marconi · Jan 8, 2023

marconi said:
Ok, Try implementing the circuitry below for each Q output. It will produce for each Q output the option of sinking or sourcing current. Your DTL logic gates require for some inputs to be sourced and for the other to be sinked. I have illustrated this.

This is for your dtl design.

_q12x_ · Jan 8, 2023

So, check this out
I tested some more in reality and nothing worked.
What it did worked, my 555 super dupper cct, but directly on the pins of the 7493-not on the diodes and when the counting was over the pin I connected. So if it was counting to 8, my 555 was getting an impulse and its led on pin 3 was lit for the duration (delay) I make it to work.
So after some more failures, I decided to get rid of all those damn diodes because whatever I was doing I couldnt get any signal from them. This is it.
Instead, I BELIEVE, I did it the proper way now. I connected 4 leds directly to the 4Q's of the 7493 to gnd. I know it should be inverse, from + to Qpin, and I did it like that, but the leds were litting inversed. So I had to put them to gnd. Sourcing through the 7493 pin instead of sinking.
The good news is that now I have those 4 leds litting in binary - perfectly !
But I do not have that 4 input AND gate that I made from all those 4 diodes. You understand what I was doing now?
And thats not the only problem. I will need... probably 2 or 3 AND gates with 4 inputs, 1 here in the binary logic, and others in the display # LEDs. Aaaah.... When you dont have what you need.... hard stuff. I really thought I will pull it out with the diodes. Im so dissapointed....

marconi · Jan 8, 2023

There were two suggestions for you to try.

_q12x_ · Jan 8, 2023

I happen to have only 1 one:
CDB430E Romania 1979 IPRS Baneasa equivalent to SN7430N 8-Input Positive NAND Gates
And that will pe good enough for the logic side.
But for the others.... thats why I got into great length, doing it with diodes.
I will built what I can, and leave what I can not make as a hole and put a label there "complicated".
But I will be able to make it work to a point. We'll see.
Im happy I find this 8 input NAND gate. I will have to transform it into a AND to do the proper job and every other pins will have to be linked to +5V (High).

I also have:
CDB410E x2 Romania 1980 IPRS Baneasa equivalent to SN7410N Triple 3-Input Positive NAND Gates
They may be handy.... Also I will have to transform them into AND gates as well.
We will see.
I also have
CD4081BE x20 AND gates
But until I will commit to the display module, I have to finish this logic side with 8 input NAND gate/transformed into an AND.

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